Bacteria 'skin' helps assemble metal nano-clusters

Bacteria 'skin' helps assemble metal nano-clusters

来源：未知 作者：檀羌筋 时间：2019-03-02 08:09:03

By Tom Simonite (Image: Sonja Selenska-Pobell/Mohamed Larbi Merroun) A defence mechanism used by bacteria to avoid poisoning by heavy metals has been harnessed for the construction of atomic-scale “nano-clusters”. These tiny structures, made from atoms of platinum, palladium and gold, could be used to make more efficient catalysts or nano-electronic components, say the researchers involved. Researchers at the Rossendorf research centre in Dresden, Germany, used the bacteria Bacillus sphaericus to produce the nano-clusters. The organism can survive in soil contaminated with heavy metals thanks to a protective coating of proteins and sugars known as the S-layer. The bacteria’s S-layer is covered with 8-nanometre-wide pores that allow nutrients through but prevent heavy metals from poisoning the cell beneath. Proteins inside the pores bind metal ions together which can later be assembled into nano-clusters of pure metal. Pollman and colleagues first chemically stripped the S-layer from each bacterial cell. They then added a solution containing metal ions which bind onto the proteins just inside the pores. Finally, hydrogen was added, which encouraged the atoms to form tiny clusters inside the pores, comprised of 50 to 80 metal atoms each. The team has identified the amino acids in the protein that bind to the metal ions. By altering these, they believe them may ultimately be able to create custom-made nano-clusters using the bacteria. It might be possible to produce clusters of a range of materials, or even different shapes, Pollman says. The team created nano-clusters that could potentially be useful in engineering. Small metallic clusters are already widely used in the catalysts that speed chemical reactions in batteries, for example. “It works very well,” researcher Katrin Pollmann told New Scientist: “The S-layer can make nano-clusters from metals including palladium, platinum or gold.” “This is the first step in trying to modify the clusters the S-layer produces,” Pollman explains. “We are planning to modify the genes to change the amino acids and enhance or alter how metals bind.” Lee Cronin at Glasgow University, UK, says the approach could provide an important new tool for nano-assembly. “People are always trying to find ways to make things from the bottom up instead of the top down,” he says “This is a fine example of how biology can be used to achieve that.” Evolution has refined biological systems to make them more efficient than tools built by humans, Cronin says. He also thinks the German researchers’ nano-clusters might prove most useful in electronics. “Clusters with such small numbers of atoms could have very interesting electrical properties,